Composition and Diversity of Soil Microbial Community Associated With Land Use Types in the Agro-Pastoral Area in the Upper Yellow River Basin

Abstract

The microorganisms of soil are sensitive to their living microenvironment, and their community structure and function will change with the environmental conditions. In the agro-pastoral area on the Qinghai-Tibet Plateau, revealing the diversity of the soil microbial communities and its response to different soil physicochemical properties and environmental factors are important for ecosystem management. The microbial (bacteria and archaea) community composition and diversity under different land use types (cultivated land, grazing grassland and planted forest) were analyzed by 16S rRNA (V4 region) method in a typical agro-pastoral region in the upper Yellow River basin. Also, the soil nutrients were studied and correlated with the microbial community. The results showed that the soil nutrient contents in grassland were low, but the available nutrients were relatively high. There was a great spatial variability under different distances to the river. The microbial community diversity was lower in the grassland than the cultivated land and forest land closer to the river. For all land uses, the dominant phyla of soil microorganisms included Proteobacteria, Actinobacteria, and Bacteroidetes, while the abundance of Clostridia was significantly higher than that of the other groups, indicating that Clostridia dominated the Firmicutes and affected soil microbial community composition. The linear discriminant analysis (LDA) effect size (LefSe) analysis showed different biomarkers were more abundant in grassland than other land use types, suggesting that the structure and diversity of soil microorganisms in grassland were significantly different compared with cultivated land and forest land. The distance-based redundancy analysis (db-RDA) results showed that the total phosphorus (TP) and calcium (Ca) were the key environmental factors affecting the diversity and abundance of the soil microbial community in cultivated land and forestland, respectively. However, the microbial diversity in grassland was more related to spatial distance of the river. These results provided a theoretical basis for the changes in the composition, structure, and function of soil microbial communities in agro-pastoral areas.

Keywords: agro–pastoral area; microbial community composition; soil microbial diversity; soil property; spatial distribution.

FIGURE 1

Study area and sampling site.

FIGURE 2

Principal coordinate analysis (PCoA) analysis of sampling points based on unweighted unifrac distances of microbial communities. Each point represented a sample, the same color was the same sampling area.

FIGURE 3

Heatmap of beta diversity index. C1: cultivated land with distance to river from 100 to 200 m; C2: cultivated land with distance to river from 300 to 500 m; G1: grassland with distance to river from 100 to 200 m; G2: grassland with distance to river from 300 to 500 m; T1: forestland with distance to river from 100 to 200 m; T2: forestland with distance to river from 300 to 500 m.

FIGURE 4

Microbial community composition at different levels: (A) phylum, (B) class, and (C) classified genus (top 35). C1: cultivated land with distance to river from 100 to 200 m; C2: cultivated land with distance to river from 300 to 500 m; G1: grassland with distance to river from 100 to 200 m; G2: grassland with distance to river from 300 to 500 m; T1: forestland with distance to river from 100 to 200 m; T2: forestland with distance to river from 300 to 500 m.

FIGURE 5

Linear discriminant analysis (LDA) effect size (LefSe) analysis of soil microbial abundance. C1: cultivated land with distance to river from 100 to 200 m; C2: cultivated land with distance to river from 300 to 500 m; G1: grassland with distance to river from 100 to 200 m; G2: grassland with distance to river from 300 to 500 m; T1: forestland with distance to river from 100 to 200 m; T2: forestland with distance to river from 300 to 500 m.

FIGURE 6

Distance-based redundancy analysis (db-RDA) of soil physicochemical properties with microbial community at phylum level. C1: cultivated land with distance to river from 100 to 200 m; C2: cultivated land with distance to river from 300 to 500 m; G1: grassland with distance to river from 100 to 200 m; G2: grassland with distance to river from 300 to 500 m; T1: forestland with distance to river from 100 to 200 m; T2: forestland with distance to river from 300 to 500 m.